Apparatus for recovering marketable products from scrap rubber

ABSTRACT

Tire pyrolysis systems and processes are provided which include feeding tire shreds to a pyrolysis vessel ( 40 ) and pyrolyzing the shreds in a pyrolysis vessel ( 40 ) to produce a pyrolysis gas and carbon black mixture. The pyrolysis gas processed by centrifugally separating entrained particles therefrom, separating the pyrolysis gas into a hydrocarbon condensate and a light vapor, removing entrained hydrocarbon condensate from the light vapor, and purifying and refining the hydrocarbon condensate. The carbon black mixture is processed by pulverizing the mixture to break up all strands and clumps of inorganic solids, cooling the carbon black mixture, separating the gross contaminants from the carbon mixture, and purifying and refining the carbon black. The hydrocarbon condensate is purified and refined by removing all remaining contaminants, removing any polycyclic aromatics to produce a clear, colorless plasticizer oil. The carbon black is purified and refined by pulverizing it into a powder, removing all remaining particulate contaminants, optionally pelletizing the carbon black, and bagging or packaging it for shipping.

CROSS-REFERENCES TO RELATED APPLICATIONS

This patent application claims the benefit of U.S. ProvisionalApplication No. 60/236,519, filed Sep. 29, 2000, of the same or similartitle.

BACKGROUND OF THE INVENTION

The present invention relates generally to methods and devices forpyrolyzing scrap materials having a high hydrocarbon content and forrecovering marketable end products from the pyrolysis of thesematerials. More specifically, it relates to a system for pyrolyzingscrap rubber shreds and refining the pyrolysis by-products to producehigh quality carbon black and plasticizer oil.

Modern society is producing ever increasing amounts of scrap materialshaving a high hydrocarbon content. Certain scrap material originatesfrom commercial products that have generally been produced throughindustrial processes requiring hydrocarbon-containing natural resourceswhich may be either renewable (such as forest products) ornon-renewable, such as petroleum, oil, and coal. Disposal of such scrapmaterials presents a problem. They must either be dumped as landfill,put into the ocean, or decomposed/destroyed in some manner. Each ofthese alternatives presents its own problems; however, the lattersolution has the advantage that the end products from suchdecomposition/destruction may have further commercial value which mayjustify the cost of the process economically. It is highly desirable tofind a way in which to efficiently recover valuable materials from suchscrap materials in order to reduce the environmental pollutants whichresult from their decomposition/destruction.

Scrap material of particular concern is the disposal of automobiletires. In the United States alone approximately 350 million tires arediscarded annually. Most of these tires are quartered or shredded andthe shreds are sent to land fills after being quartered or shredded.Such shreds constitute about two percent of solid waste in the UnitedStates and about 164 million cubic feet per year of land fill space.Moreover, since these shreds are composed of hydrocarbon materials andhydrocarbons are a principle source of energy, the buried tiresrepresent over 90 million MMBTU's per year of wasted energy. Analternate method of disposing of scrap tires is to burn them. This doesrecover about one-third of the economic value in terms of carbon blackand generated energy. However, this method of disposal is not efficient,and it produces environmental pollutants.

Unfortunately, the rubber from scrap tires cannot be recycled directlyinto the manufacture of new tires because of the different types ofrubber involved. A small portion, about 15 percent, of the scrap tirerubber can be recycled as tire chips for use in various end productssuch as matting and road surface compositions. However, this disposalmethod is limited in the amount of scrap rubber that can be processed.It is also relatively expensive due to the amount of liquid nitrogen thechip recycling process requires.

Pyrolysis offers great promise for disposal of hydrocarbon-containingscrap materials generally and scrap tires in particular. Pyrolysisprovides an efficient, cost effective method for processing largevolumes of scrap rubber and recovering marketable end products.Conventional scrap rubber pyrolysis produces two end products. First, itproduces a coarse and impure grade of carbon black requiring furtherprocessing before it can be reused. The impurities are generally thesteel used in the tire carcass, sulfur used in the vulcanization of therubber, some zinc, and other trace materials. Second, scrap rubberpyrolysis produces a pyrolysis gas having a heavier weight hydrocarbonfraction and a lighter weight hydrocarbon fraction. The heavier weighthydrocarbon fraction, which is condensed as a liquid from the pyrolysisgas, is a low grade oil suitable as fuel oil. The lighter weighthydrocarbon fraction remaining in a vapor state has little value and cantypically be recycled back through the pyrolysis process as fuel for theburners; it can also be sold as fuel under certain special circumstancesor simply flared to the atmosphere.

Pyrolysis of tire shreds presents several unique problems. First, thepyrolysis gas exiting from the pyrolysis system contains entrainedcarbon black particles which are difficult to remove during thecondensation of the pyrolysis gas into its liquid and vapor fractions.Second, it is difficult to obtain a consistent hydrocarbon condensatecomposition when condensing the pyrolysis gas into its liquid and vaporfractions. Third, because carbon black has a high affinity for gasses,it frequently contains an excess of pyrolysis gas which is adsorbedwhile it is still in the pyrolysis system; this presents problems in thefurther refinement of the carbon black.

It can be seen that a generic model for a Hydrocarbon Recovery Systemcan be considered as being composed of the following three subsystems: aPyrolysis System, a Gas Processing System, and a Solids ProcessingSystem. The Pyrolysis System receives the hydrocarbon-containingmaterial and breaks down the material into a hydrocarbon-containingpyrolysis gas and a solid by using of intense heat in the absence ofoxygen. The system may include a input component for handling the inputmaterial and delivering it to the pyrolysis process components; it mayalso include a removal component for providing the pyrolysis gas andsolids in a pre-processed form to other systems for further refinement.The Gas Processing System refines the liquid fraction of the pyrolysisgas to produce usable end products. The Solids Processing System refinesthe impure carbon black provided by the Pyrolysis System to produce ausable form of carbon black, depending upon the application. Accordingto this model, it should be noted that the division of functions betweenthe Gas/Solids Processing Systems and the Pyrolysis System removalcomponent is highly dependent as a practical matter upon the allocationof functions between these two areas. This functional allocation canalso depend upon the physical configuration of the components and howthey are laid out within the facility.

The Hydrocarbon Recovery System can be generally characterized as acontinuous system where the input materials are provided in a more orless continuous rate, rather than in batches, and the products areproduced at a continuous rate. It is intended to process feed stockscomposed of fairly homogeneous hydrocarbon materials, generallydescribed as waste or scrap products. These feed stocks take the form ofscrap rubber produced from used automobile tires which have beenshredded; coal or shale having a high sulfur content coal and shale; orforest products such as tree bark, waste lumber, leaves, branches, etc.Ideally, the Hydrocarbon Recovery System will process such materials inan energy efficient, cost effective manner which is environmentally safewith regards to the marketable materials produced and the byproducts ofthe process, e.g. exhaust gases, pyrolysis vapor, heated coolants,removed contaminants, etc. Such a system will provide end products whichare marketable, recoverable, and economical.

BRIEF SUMMARY OF THE INVENTION

According to the model described heretofore, the present inventionprovides a Hydrocarbon Recovery System for scrap rubber in the form ofscrap tire shreds, which includes a Scrap Rubber Pyrolysis System, aCarbon Black Refinement and Purification System and a Plasticizer OilPurification System. The Scrap Rubber Pyrolysis System produces aselected hydrocarbon condensate from the pyrolysis gas and a crudecarbon black containing inorganic impurities but which is essentiallyfree of adsorbed pyrolysis gas. The Carbon Black Refinement andPurification System mills and purifies the carbon black to produce a lowstructure furnace black. This low structure furnace black has a muchgreater market value than the low grade carbon black produced byconventional pyrolysis and has a variety of commercial applicationsincluding the production of inks and adhesives, for example. ThePlasticizer Oil Purification and Refinement System produces a clear,colorless oil or “bright stock” which is marketable as a plasticizer andextender oil for rubber and plastic compounding processes. Thisplasticizer/extender oil has a considerably higher market value than thefuel grade oil produced by conventional pyrolysis methods.

It is thus an object of this invention to provide an improved ScrapRubber Pyrolysis System for pyrolyzing scrap rubber provided from tireshreds.

It is a further object of this invention to provide an improved ScrapRubber Pyrolysis System which provides pyrolysis gas which isessentially free of entrained carbon black particles.

It is a further object of this invention to provide an improvedPlasticizer Oil Purification and Refinement System for the recovery of aselected hydrocarbon condensate fraction from pyrolysis gas for use asplasticizers and solvents.

It is a further object of this invention to provide an improvedPlasticizer Oil Purification and Refinement System which provides anenvironmentally safe plasticizer/extender oil which is free ofpolycyclic aromatics.

It is a further object of this invention to provide an improved CarbonBlack Purification and Refinement System for the production of highgrade carbon black.

It is a further object of this invention to provide an improved CarbonBlack Purification and Refinement System for the production of highgrade carbon black in the form of soft pellets.

These and other objects of the invention may be more clearly seen fromthe detailed description of the preferred embodiment which follows.

BRIEF DESCRIPTION OF THE DRAWINGS

The foregoing summary, as well as the following detailed description ofthe preferred embodiments of the invention, will be better understoodwhen read in conjunction with the appended drawings. For the purpose ofillustrating the invention, there are shown in the drawings embodimentswhich are presently preferred. It should be understood, however, thatthe invention is not limited to the precise arrangements andconfigurations shown. In the drawings, like numerals are used toindicate like elements throughout. In the drawings:

FIG. 1 presents a block diagram showing the generic model for aHydrocarbon Recovery System with its three subsystems and their outputs.

FIG. 2 presents a block diagram of the Scrap Rubber Pyrolysis System.

FIG. 3 presents a detailed block diagram of an embodiment of the ScrapRubber Pyrolysis System showing its components and how they interact.

FIG. 4 presents a detailed block diagram of an embodiment of thePlasticizer Oil Purification and Refinement System showing itscomponents and how they interact.

FIG. 5 presents a detailed block diagram of an embodiment of the CarbonBlack Purification and Refinement System showing its components and howthey interact.

DETAILED DESCRIPTION OF THE INVENTION

The present invention is directed to a Scrap Rubber Recovery System forrecovering marketable end products from scrap rubber. It consists ofthree subsystems. First, it includes a Scrap Rubber Pyrolysis System forbreaking down a feed stock of tire shreds into its constituent parts,namely, a pyrolysis gas comprised of volatile hydrocarbons andgranulated carbon black containing inorganic impurities without adsorbedpyrolysis gas. The pyrolysis gas is provided essentially free ofentrained carbon black particles and is further broken down into aselected hydrocarbon condensate fraction and a vapor fraction. Second,it includes a Carbon Black Purification and Refinement System whichfurther refines and purifies the granulated carbon black to produce ahigh grade of carbon black for use in inks, rubber products, and thelike. Third, it includes a Plasticizer Oil Purification and RefinementSystem which further refines and purifies the hydrocarbon condensate toproduce a high grade of plasticizer/extender oil, or “bright stock”,from which has been removed polycyclic hydrocarbons which are consideredto be environmentally hazardous.

A. Scrap Rubber Pyrolysis System

This system and method processes a feed stock, preferably consisting ofwaste products, having high hydrocarbon content by breaking it down intoconstituent parts consisting primarily of crude carbon black havinginorganic contaminants and a pyrolysis gas comprising a mixture ofvolatile hydrocarbons. When the feed stock consists of scrap tireshreds, the desired end products consist of commercially marketablecarbon black and plasticizer oil.

It has been found that a closed, steady state system is preferred topractice the pyrolysis process, meaning that a measured, metered inputof raw material of known composition provided in the absence of oxygenis input to the system, a constant amount of heat is applied to thematerial under constant pressure conditions for a constant residencetime, and the end materials are removed from the system at a constantrate, with the residence time and input rate of raw material chosenaccording to the volume of the reaction vessel. This is bestaccomplished by passing the material as a slowly moving bed through apyrolysis vessel, with different parts of the bed at different stages ofthe overall pyrolysis process. No extraneous materials or end productsare reintroduced back into the system since this would change the steadystate composition of the system. It is essential to maintain an eventemperature throughout the pyrolysis vessel by eliminating temperaturegradients within the vessel. To establish the necessary beginningconditions for the maintenance of a steady state system, the system ispurged with nitrogen and brought up to temperature before the inputmaterial is introduced.

Pyrolysis in general is the process of breaking down a hydrocarbonmaterial in the absence of oxygen into its constituent parts, namely,forms of carbon and various hydrocarbon compounds having a broad rangeof molecular weights. The percentage distribution of differenthydrocarbon compounds depends upon the temperature at which they areproduced, inasmuch as higher temperatures tend to result in a mixturehaving greater percentages of lower molecular weight hydrocarboncompounds and lower temperatures tend to result in a mixture havinggreater percentages of higher weight hydrocarbon compounds. This is duein part to the process known as “cracking”, where high temperatures areused to decompose or break long hydrocarbon chains into shorter chains.It should be recognized that, if the pyrolysis temperature issufficiently high, the pyrolysis temperature will directly affect thedistribution of hydrocarbons within the resultant gas/liquid resultingtherefrom.

Thus it can be seen that a judicious choice of pyrolysis temperature canresult in not only the decomposition of a given feed stock but also in apredictable distribution of resultant hydrocarbon byproducts resultingfrom the pyrolyzation of that feed stock. For example, if the feed stockconsists of shredded automobile tires, then the plasticizer oil used bythe manufacturer to give the tires their elastometric qualities can berecovered for reuse since such plasticizer oil consists of a knownpercentage mixture of hydrocarbon products.

Efficient separation of these end products from one another has beenheretofore difficult to achieve. When the feed stock is introduced intothe pyrolysis reactor at the selected pyrolysis temperature, it israpidly broken down into a pyrolysis gas comprised of volatilehydrocarbons and carbon black containing inorganic impurities. Since itis well known that carbon has an affinity for gases (as evidenced by thefact, for example, that activated charcoal is used in air filtrationsystems), the pyrolysis gas tends to adhere to the surface of the carbonblack component of the solid end product by the process known asadsorption. When that end product is removed, it is thus contaminatedwith hydrocarbon compounds which must be removed in the subsequentrefinement process. Such removal is costly, time consuming, andneedlessly complicates the carbon refinement process. It is desirable toremove as much of these surface hydrocarbon compounds as possible beforethe carbonaceous material leaves the reactor.

Furthermore, the pyrolysis gas must be removed as an end product fromthe reactor as well. The flow of pyrolysis gas to the exit port of thereactor allows the gas to pick up carbon black particles which arethereby entrained within the exiting pyrolysis gas. These entrainedparticles tend to complicate and interfere with the proper operation ofliquid filtration equipment and necessitate more frequent changes offiltration means. Removal of such carbon black particles is more easilyperformed while the pyrolysis gas is still in a gaseous state than whenit is in a liquid state. The presence of entrained particles can thusneedlessly complicate the refinement process for the pyrolysis gas.These entrained particles can be reduced in quantity by reducing oreliminating the agitation of the moving bed of material being pyrolyzed;by reducing the velocity of the exiting pyrolysis gas; or by removal ofthe particles while the pyrolysis gas is in a gaseous state. Preferably,all three methods are used.

The pyrolysis process employed by the invention enables the engineer toreliably predict the quantity and composition of the resultanthydrocarbon end products. As an added benefit, the carbon black endproduct contains little or no hydrocarbon residue on the surface of thecarbon black particles, thus simplifying subsequent refinement processesfor the carbon black. Such carbon black end products can be easilyrefined to produce carbon black of sufficient quality for direct reusein automobile tires and other rubber products. With a differentrefinement method, this end product can be further purified andprocessed to produce toner black for use in copying machines andprinters employing a xerographic process. The quality and composition ofthe end products produced by the Scrap Rubber Pyrolysis System must beconsistent in order to design efficient industrial processes toefficiently purify and refine these end products.

To achieve the desired degree of predictability, the temperature withinthe pyrolysis vessel at which the feed stock is pyrolyzed must beconstant with a permissible variation of ±0.1%. Furthermore, the entirepyrolysis process must achieve a steady state condition, which means thefollowing:

-   -   a. The feed stock is input at a constant feed rate;    -   b. All materials must move through the pyrolysis vessel in a        moving bed at a constant, controlled rate, so that all parts of        the bed are exposed to the constant temperature for the same        amount of time;    -   c. The end products are removed from the pyrolysis vessel at a        constant rate; and,    -   d. No end products are reintroduced into the pyrolysis vessel        for further processing.

The two end products, hydrocarbon gasses and carbon black, must beseparated as completely as possible within the pyrolysis vessel; thatis, the carbon black upon exit from the Scrap Rubber Pyrolysis Systemmust have little or no hydrocarbon adhering to the surface of itsparticles.

These characteristics implemented by the present invention represent asurprising and nonobvious result over the prior art which has heretoforeemphasized the use of multiple heating zones with different temperaturesor special burner configurations to achieve a gradual increase/decreasein temperature over the length of the moving bed. It must also berecognized that the pyrolysis process described in the prior artactually consists of two separate and distinct steps: (1) the actualpyrolysis of the hydrocarbon feed stock into its two end products,carbon black containing inorganic contaminants and pyrolysis gascomprising volatile hydrocarbons; and (2) the complete separation ofthese two end products from one another to simplify subsequentrefinement and purification of each end product.

The prior art teaches, either explicitly or by implication, that thepyrolysis process takes place during the entire residence time of thematerial within the reactor and that the final carbonaceous solids areremoved only when pyrolysis is complete. The prior art also teaches,either explicity or by implication, that the moving bed must be agitatedin order to thoroughly expose the feed stock and promote more completepyrolysis. In actuality, pyrolysis takes place very rapidly during aninitial time period (i.e. pyrolysis time) during which the feed stock isbroken down into impure, granulated carbon black material containinginorganic impurities and volatile hydrocarbons in a gaseous phase.However, carbon black has a strong affinity for hydrocarbons, and asignificant quantity of the hydrocarbons are adsorbed by the carbonblack within the pyrolysis vessel. Over time, these adsorbedhydrocarbons must be desorbed in order to improve the quality of thefinal carbon black product (i.e. desorption time). It is this divisionof time between pyrolysis time and desorption time which has beenunrecognized in the prior art. The adsorbed hydrocarbon is released by asufficient residence time of the carbon black in a steady stateenvironment having a constant temperature. Furthermore, carbon blackparticles are entrained in the hydrocarbon gas by agitation of thecarbon black. Such entrained carbon black particles must be removedlater in the process before efficient refinement of the hydrocarbon gascan take place. It is desirable to leave the carbon black undisturbedduring its residence time, since nearly complete desorption will takeplace for a desorption time of sufficient duration. As a compromise, asystem is required to gently move the carbon bed through the reactionzone without undue agitation of the carbon black so that entrainedparticles are reduced within the hydrocarbon gas while at the same timeallowing the carbon black to desorb its adsorbed hydrocarbon gascomponent.

This important fact, i.e. the bifurcation of the residence time into apyrolysis time and a desorption time, along with other features andinnovations which shall become evident herein, is employed in theimproved and efficient pyrolysis method and apparatus of the presentinvention. A steady state system allows the hydrocarbon compounds to bedesorbed from the carbon black in the moving bed by retaining the solidswithin the reactor at the elevated temperature for a sufficient timeperiod. Also, by gently moving the bed of feed stock through the reactorwhile at the same time reducing the velocity of the pyrolysis gas withinthe reactor so as not to disturb the surface of the moving bed, theamount of entrained solid material within the exiting pyrolysis gas isreduced to a small amount.

Referring now to the drawings in detail, FIG. 2 presents a block diagramof the Scrap Rubber Pyrolysis System 10, showing an input means 11, aprocessing means 12, and a removal means 13. The function of the inputmeans 11 is to deliver scrap rubber 5 to the processing means at acontrolled rate under conditions excluding oxygen therefrom. Theprocessing means 12 functions to perform destructive distillation of thescrap rubber 5 and to thus decompose it into solids and gases.Processing means 12 is a steady state system having only one input,namely the scrap rubber 5 provided by the input means, and one output,namely the end products of the pyrolysis and desorption process. Theremoval means 13 functions to remove gross contaminants from the endproducts of the processing means to produce gas, hydrocarbon condensate,and crude carbon black. These outputs are in a form to allow them to befurther refined by other systems in an efficient and cost-effectivemanner, depending upon the desired end product.

Referring now to the drawings in detail, FIG. 3 presents a schematicflow diagram of the components of the Scrap Rubber Pyrolysis System ofthe present invention. The flow of material through the system isgenerally from left to right and the outputs from the system are givenon the right, according to the figure.

Scrap rubber 5 is provided to the system in the form of tire carcasseswhich are shredded, or comminuted, by shredder 20 which shreds the scraprubber material into suitably sized fragments for pyrolysis. As usedherein, the term “shredder” denotes any of a variety of size reductiondevices which produces any shape of pieces of fragments. Similarly, theterm “shred” denotes any size or shape of fragment which is acceptableby the Scrap Rubber Pyrolysis System. Preferably, shreds having a majordimension of about 2 inches are preferred. Oversized shreds mayoptionally be removed and fed back into shredder 20 to enhanceuniformity of the shred size. For purposes of the invention, shreds mayeither be produced off site and delivered to the location of the systemor else the shreds may be produced on site.

The shreds are introduced into the system by means of a weigh beltconveyor 21 which controls the rate at which shreds are delivered. Thespeed of weigh belt conveyor 21 is responsive to the weight of theshreds placed thereon to maintain a constant flow of shred mass. Ahopper (not shown) may be employed to feed the shreds to weigh beltconveyor 21 by gravity to further promote uniformity of flow. A conveyor23 receives the shreds from the weigh belt conveyor 21 at its input end25 and delivers them at its output end 26 to the input end 27 of adeoxygenator 30. A hopper 22 may be used to funnel the shreds intoconveyor 23. As shown in FIG. 3, conveyor 23 is in the form of an augerconveyor driven by motor 28. When horizontal floor space is at apremium, a bucket or flight conveyor is used instead of an augerconveyor to deliver shreds vertically from the weigh belt conveyor 21 tothe input end 27 of deoxygenator 30. A hopper (not shown) at input end27 may be employed to facilitate entry into deoxygenator 30.

Deoxygenator 30 receives shreds at its input end 27. It is designed toremove oxygen from the shreds by passing the shreds through a pluralityof heated, non-jamming air locks 35, 36, and 37 vertically arranged sothat the apparatus forms a gravity packed feed column. The air locks 35,36, and 37 are separated by flap gates or sliding gates which open andclose in sequenced manner to deliver the shreds to the output end 31 ofdeoxygenator 30 in a manner effectively excluding oxygen. A quantity ofnitrogen is injected into the material in the middle air lock 36 todisplace the lighter molecular weight oxygen. The nitrogen gas isinjected at positive pressure to ensure that no oxygen leaks throughincomplete seals within the deoxygenator 30.

The primary portion of the Scrap Rubber Processing System is theprocessing means for pyrolysis and desorption. The scrap rubber shredsare decomposed through the process of pyrolysis, or destructivedistillation, into pyrolysis gas and crude carbon black end products.The pyrolysis gas is comprised of both light and heavy hydrocarbonvolatiles. The lighter volatiles can be recycled as fuel for pyrolysissystem, marketed as fuel grade gas in certain specialized applications,or flared to the atmosphere, whereas the heavier volatiles are condensedfrom the pyrolysis gas as useful products for remarketing, such as highgrade plasticizer oil. The crude carbon black contains only inorganicimpurities such as fiberglass fibers and metal fragments, as well assmall amounts of sulfur and zinc compounds; all organic impurities suchas nylon or polyester are decomposed by the pyrolysis process.

Pyrolysis vessel 40 is comprised of an inner pyrolysis chamber 43defined by a elongate vessel 45. Elongate vessel 45 is a cylindricalcontainer composed of stainless steel which has a high coefficient ofheat transfer and is designed to withstand high temperatures for longperiods of time. Alloys containing high percentages of chromium andmolybdenum are preferred. The output end 31 of deoxygenator 30 is indirect communication with the interior pyrolysis chamber 43 throughconduit 41.

A screw conveyor mounted axially inside elongate vessel 45 comprises ashaft 47 supporting appendages 48 arranged in a broken helix patternthereon. The appendages may be spikes, paddles, blades, or some otherelongate device of similar design. Shaft 47 rotates on sealed bearings(not shown) which prevent outside air from entering the vessel. As shownin the drawing, motor 50 provides the rotational motion for shaft 47;however, other means of providing rotational motion may be used withoutdeparting from the intent of the invention, such as chain drives and thelike. The rotational rate provided by motor 50 controls the residencetime of the moving bed within elongate vessel 45. The purpose of thisscrew conveyor is to move the bed of material from the input end 44 tothe output end 49 of elongate vessel 45 as shaft 47 is rotated.Additionally, appendages 48 gently agitate the bed to expose all partsof the bed to the internal atmosphere in pyrolysis chamber 43 in orderto promote desorption of pyrolysis gas from the solids in the bed and toprevent hot spots. Care must be taken to prevent excess particles frombeing entrained in the pyrolysis gas within the pyrolysis chamber 43 bytoo much movement of the bed. Agitation is not required or necessarybut, as a practical matter, serves to allow shorter pyrolysis vesselsand reduces the time required for the moving bed to traverse elongatevessel 45.

The heat for the pyrolysis reaction occurring in the inner pyrolysischamber 51 is supplied by combustion which occurs inside a heatingchamber 51 defined by a refractory lined furnace box 52 which surroundsthe elongate vessel 45. The furnace box 52 is equipped with multipleburners 55 which burn fuel gas in the heating chamber 51. Burners 55 aredesigned to provide a constant temperature within the entire length ofelongate vessel 45 by minimizing temperature gradients within the innerpyrolysis chamber 43. Environmental considerations dictate that theamounts of NOX emissions be minimized or eliminated. In order toeliminate such NOX emissions, an overabundance of air is supplied to theburners by means of blower 56. Because of velocity considerations, thefuel supplied to burners 55 is also supplied by means of a blower 57.The fuel/air mixture is adjusted so that the increased supply of oxygento the flame cools its temperature to below 2000° F., below which NOXdoes not form. The resulting exhaust gases are thus free of NOX and canbe released into the surrounding atmosphere as by a smoke. These exhaustgases are not suitable for use in other parts of the process. The highoxygen content of the exhaust gases make them unsuitable for purposes ofpressurization in other portions of system, since the excess oxygen maycause hot solids to ignite. A thermocouple control mechanism (not shown)is used to automatically regulate the burners according to the internaltemperature of pyrolysis chamber 43. It has been found that athermocouple control mechanism has a number of advantages over the olderinfrared means for measuring temperature. First, the thermocoupleprovides more accurate temperature readings than infrared means. Second,it eliminates the requirement for a sight port in the wall of pyrolysisvessel 45. Third, it is easily integrated into modern digital controlsystems for automatic monitoring of system functions.

The crude carbon black resulting from pyrolyzation of shreds collects atthe output end 49 of pyrolysis vessel 45. Carbon black output port 60 islocated at the bottom of pyrolysis vessel 45 at its output end 49 toreceive the crude carbon black as a gravity packed column. A rotaryvalve 62, also known as a “star valve”, serves as both an air lock and aregulator for the removal of crude carbon black. Under control of aautomated control system, the rotational rate of the rotary valve 62 canbe controlled to deliver a constant flow of crude carbon black out ofthe pyrolysis vessel. Weir 61 encircles the upper end of carbon blackoutput port 60 to further control the amount of crude carbon blackfalling therein.

The crude carbon black exiting pyrolysis vessel 45 is composed ofvarying sized clumps of carbon black, fiberglass strands, and otherinorganic contaminants. Pulverizing these clumps immediately upon exitfrom pyrolysis vessel 45, rather than later in the process aftercooling, has been found to have a number of benefits. First, the clumpscan be reduced in size to particles which are relatively uniform. Thisenables other devices in the purification process to operate moreefficiently without frequent cleaning or jamming. Second, breaking upthe fiberglass strands which may have agglomerated (“birds nests”) intosmaller pieces prevents; such birds nests are known to cause auger-typeconveyors to bind. Removing the possibility of birds nests allows theengineer to design a more efficient carbon black purification system.Third, pulverization increases the surface area of the total mass topromote more rapid cooling and to break free any gross contaminantswhich might be mechanically attached to the carbon black. A hammer mill63 is provided with an inlet 64 in communication with carbon blackoutput port 60 through rotary valve 62. The hammer mill 63 functions asa sizing means to break up any large pieces in the stream of crudecarbon black and to reduce the stream to a smaller, more uniformparticle size. All inorganic strands of fiberglass, steel, and othermetals are broken up into much smaller pieces thereby, so that theproblem of producing “birds nests” of fiberglass fibers is eliminated.This result has the unexpected design advantage that subsequentequipment can be designed more simply and efficiently since the birdsnest problem is not a consideration.

The output 65 of hammer mill 63 is in direct communication with theinput 66 of the carbon black conveyor/cooler 67. The conveyor/cooler 67may be an auger or screw conveyor and preferably is surrounded by acooling jacket containing a heat transfer fluid such as water orantifreeze which will cool the hot carbon black as it is conveyedtherethrough. Conveyor/cooler 67 lowers the temperature of carbon blackfrom the pyrolysis temperature to around 200° F. The cooled carbon blackis then conducted through a conduit to a carbon black screening assembly68 to remove oversized and ferrous contaminants from the cooled carbonblack. The screening assembly 68 comprises a screening device 70 whichseparates and removes oversized fragments and gross contaminants, suchas fiberglass filaments and larger bits of ferrous material, from thecarbon black. The magnetic separator 69 separates and removes anyferrous contaminants such as metal particles which remain. It is of adrum type, such as the Grizzley EREIZ Mechanical Separator commonly soldby such companies as Eriz Magnetics, Erie, Pa. It should be noted thatthe order in which the screening device 70 and the magnetic separator 69are applied to the carbon black is immaterial and could be in reverseorder without departing from the spirit of the invention. Also, othermechanisms such as size metering devices or the like may be used inplace of screening device 70 without departing from the spirit of theinvention.

Pyrolysis gas generated by in the pyrolysis chamber 43 is removed fromthe chamber through the pyrolysis gas outlet conduit 42 located on theinput end 44 of pyrolysis vessel 45 adjacent to conduit 41. Exitingpyrolysis gas is known to contain particulate matter consisting ofcarbon black particles. It is desirable to reduce the amount ofentrained particles from the pyrolysis gas prior to purification sinceremoval of particles from pyrolysis gas before its hydrocarbons areseparated into lighter and heavier fractions is more economical thanremoval of particles from the condensed, heavier hydrocarbon fractionsafter separation. Hydrocarbon condensate containing carbon blackparticles forms sludge which collects on equipment interiors and must belaboriously removed. Reduction of entrained particles from gas can beaccomplished by either preventing the gas from picking up particlesinitially or else removing particles once they have become entrained. Tothis end, three methods are used to reduce the density of entrainedsolids in the exiting pyrolysis gas: (1) minimal agitation of the movingbed while it is in the vessel, (2) reduction of velocity of the gas asit exits the vessel, and (3) physical removal of all particles possiblebefore a fraction of the pyrolysis gas is condensed as a liquid.

The first method is implemented in the present invention by keeping therotational speed of shaft 47 as low as possible. The second method isimplemented by sizing the diameter of conduit 42 as large as practicalto reduce velocity of exiting gas. It is a well known principle ofphysics that the velocity of a moving fluid increases exponentially asto the diameter of its conduit. Furthermore, the amount of lightmaterial that a moving gas will pick up, or entrain, when it is flowingover the surface of the light material is directly proportional to itsvelocity. Therefore, the velocity of the exiting pyrolysis gas can bereduced by keeping the diameter of conduit 42 as large as practical,depending upon the size of pyrolysis vessel 40.

Pyrolysis chamber 43 is in direct communication with inlet 71 of thecentrifugal separation means 75 through conduit 42. Centrifugalseparation means 75 removes entrained carbon black particles from theexiting pyrolysis gas. The advantages of removing such entrainedparticles in this manner are that (1) the particles are removed beforethe pyrolysis gas is condensed and thus eliminates the sludge problem indownline components of the purification process; (2) no filtering orpacking material is necessary, thus eliminating the need to replace orclean filtering material; and (3) there is no sludge or tar buildupwithin the device itself since the pyrolysis gas is at a temperaturehigher than the boiling point of any volatile hydrocarbons present. Thismethod has been shown to remove up to 98% of entrained particles fromthe pyrolysis gas.

The device used as the centrifugal separation means 75 in the presentinvention is a cyclone separator. Although well known in other areas ofthe art, it is believed that its use in this application has heretoforebeen unrecognized and represents a new and novel approach to the problemof separating entrained particles from pyrolysis gas. The cycloneseparator is constructed as an inverted, truncated cone with the largediameter end directed upwardly and the small diameter end directeddownwardly. The pyrolysis gas tangentially enters the top, or largediameter end, through input port 71 and the gas carrying the entrainedparticles is circumferentially directed around the interior of the cone.This change in direction changes the velocity of the entrainedparticles. This change in velocity allows gravity to pull the particleslower as they circle the interior until finally they lose sufficientenergy to fall through the bottom port 73 at the small diameter end ofthe separator. The lighter pyrolysis gas is removed from port 72 at topof cyclone separator 75. Auger 74 removes the particles in a positivemanner to ensure no buildup or jamming, and they are returned to thelast air lock 37 of deoxygenator 30 where they merge with the enteringshreds. This maintains the steady state condition of the pyrolysisvessel since the amount of particles leaving the system throughentrainment within the pyrolysis gas equals the amount of particlesentering the system.

The pyrolysis gas from output port 72 of cyclone separator 75 isdirected to an oil/gas separator assembly which separates the pyrolysisgas into a heavier hydrocarbon fraction as a liquid, or oil, and alighter hydrocarbon fraction which remains in a gaseous state andcontains such hydrocarbons as methane, propane, butane, etc. Afterinitial separation, the lighter hydrocarbon fraction is fed to asecondary separator to remove any heavier hydrocarbons which remain inthe form of entrained droplets. The oil/gas separator assembly comprisesa condenser 80, a secondary separator 90, and a gas holding tank 95.

Condenser 80 is configured as a vertical cylinder with baffles 89arranged within the interior 86 and supporting internal cooling tubes(not shown). Heated pyrolysis gas is provided through gas inlet 81 atthe top of condenser 80 where is flows downwardly through interior 86 asit cools. A fraction of the pyrolysis gas condenses to form a reservoir84 of hydrocarbon condensate at the lower end of condenser 80. A liquidoutlet port 85 is provided in the bottom of condenser 80 to drain thecondensate away, and a gas outlet port 83 is provided at the lower endof the condenser to remove the lighter, gaseous hydrocarbon fraction.The level of reservoir 84 is maintained to be proximate with outlet port83. A cooling jacket 82 contains external coils which are in heattransfer relation with the sides of condenser 80 and optionally withbaffles 89 and the internal tubes. A heat transfer fluid is pumpedthrough cooling jacket 82 by pump 87. The heat transfer fluid circulatesthrough the cooling jacket 82 and internal cooling tubes to remove theheat from the heated pyrolysis gas, and then returns to a refrigerationunit 88 where it is cooled. The amount of heat transferred from theentering pyrolysis gas to the heat transfer fluid is controlled bycontrolling the rate at which pump 87 circulates the fluid.

The hot pyrolysis gas leaving the cyclone separator 75 through port 72is directed to input port 81 of the condenser 80. As it flowsdownwardly, it loses heat and the heavier hydrocarbons with high boilingpoints begin to condense and fall into the condensate reservoir 84. Thegas continues to lose heat until it reaches the bottom end of condenser80 where cooled heat transfer fluid is entering the cooling jacket 82 ata selected temperature chosen according to the required composition ofthe hydrocarbon condensate. The cooled heat transfer fluid flows incounter-direction with the entering pyrolysis gas. In this way, theequilibrium between the condensate and vapor is maintained at therequired temperature and the composition of the hydrocarbon condensateis kept consistent. The rate of heat transfer fluid flow maintains thetemperature of the liquid/gas in the vicinity of the surface ofreservoir 84 by increasing when the temperature rises and decreasingwhen the temperature falls; the temperature of the entering heattransfer fluid, however, is kept at a constant value. This method ofcondensing the heavier hydrocarbon condensate from the pyrolysis gas byprecisely controlling heat transfer fluid flow rate and temperature isbelieved to be new and unique within this area of the art.

The hydrocarbon condensate collected in reservoir 84 is removed throughliquid output port 85 and transferred to liquid holding tank 105 (FIG.4) either in preparation for shipment elsewhere or further processing inthe Plasticizer Oil Purification and Refinement System. The lightergaseous hydrocarbon fraction is removed from condenser 80 through outputport 83 after flowing over the surface of reservoir 84 and entrainingdroplets of the heavier hydrocarbon condensate. To remove this entrainedcondensate, the exiting gaseous hydrocarbon fraction is directed tosecondary separator 90.

Secondary separator 90 is constructed at a vertical cylinder with a gasinlet 91 at the bottom end and gas outlet 95 at the top end. The bottomend of secondary separator 90 forms a reservoir 93 having a liquidoutlet 92 at its lowest extent, for collecting hydrocarbon condensate.Baffles 94 are interposed in the path of the lighter hydrocarbonfraction as it enters gas inlet port 91 and flows upwardly around andthrough baffles 94 to exit through gas outlet 95. Baffles 94 areconstructed as perforated plates through which passes the lighterhydrocarbon fraction. Entrained droplets are too large to pass throughthe holes and are thus removed from the lighter hydrocarbon fraction,where they fall into reservoir 92 at the bottom of secondary separator90. The hydrocarbon condensate collected in reservoir 93 is removedthrough liquid output port 92 and transferred to liquid holding tank 105(FIG. 4) either in preparation for shipment elsewhere or furtherprocessing in the Plasticizer Oil Purification and Refinement System.

The remaining gas composed of low boiling point hyrdocarbons is takenfrom the gas exit port 95 and sent to the gas holding tank 96. There itis accumulated for use in an engine generator 97 as shown, recycled tothe burners 55, or sold as high BTU fuel gas in certain specializedsituations, or flared to the atmosphere.

B. Plasticizer Oil Purification and Refinement System

With reference now to FIG. 4, the Plasticizer Oil Purification andRefinement System of the present invention will now described. Thehydrocarbon condensate produced by the Scrap Rubber Pyrolysis System isknown to have the properties required of a input to this system,although hydrocarbon liquids from any system can be input if they havethe same general properties. The hydrocarbon condensate to be processedis transferred through conduit 102 and stored in liquid holding tank 105to be processed. Liquid holding tank 105 may receive hydrocarboncondensate from several Scrap Rubber Pyrolysis Systems which may bewithin the same facility or from any combination of such pyrolysissystems in the same or different facilities. This tank also serves as asurge tank in case of a temporary shut down in production.

The hydrocarbon condensate is transferred to a mixing vessel 120 throughconduit 110. This mixing vessel is adapted to mix the hydrocarboncondensate with a filter aid 130 under conditions which permit thefilter aid 130 to attract contaminants in the condensate. The mixingvessel 120 is equipped with a propeller type agitator device; however,any suitable means for agitation is acceptable. For automatic, regulatedfeed of filter aid 130 into mixing vessel 120, a filter aid feed system125 is used to hold filter aid 130 and weigh and dispenses the filteraid 130 at a selected rate to the mixing vessel 120 as by gravity. Thecontaminants sought to be removed from the condensate by the filter aidinclude any suspended carbon black particles which may remain within themixture; a preferred filter aid for this purpose is diatomaceous earth,and most preferably kieselguhr. The suspended particles and the filteraid form aggregates which remain as a solid in the solution.

Once the filter aid and the contaminants have formed aggregates, thehydrocarbon condensate containing the aggregates is delivered by a pump(not shown) through a conduit to a filter aid removal assembly 135 forthe removal of the aggregates. The preferred device for this purpose isa rotary drum vacuum filter which comprises a filter, vacuum pump andcondenser. The vacuum pump draws the hydrocarbon condensate into theinterior of the device, thus straining the filter aid through acylindrical, rotating filter media. A scraping blade positioned above acollection container scrapes the aggregate, or filter cake, from theoutside of the rotating cylinder where it falls into the collectioncontainer for later removal. The filter cake can be disposed of in amunicipal solid waste land fill.

The filtered hydrocarbon condensate passes through a conduit 137 intoheat exchanger 140 where it is heated in preparation for removal ofpolycyclic aromatics. Heat exchanger 140 has a standard shell-and-tubeconstruction. It receives the relatively cool hydrocarbon condensate atinlet 142, so that it passes through heat exchanger 140 and exitsthrough outlet 144. The heat transfer fluid from the carbon blackconveyor/cooler 67 having a temperature ranging from 300° F. to 400° F.is received at coolant inlet 146 where it passes through coils to heatthe entering hydrocarbon condensate, and then returns to the carbonblack conveyor/cooler 67. The hydrocarbon condensate is heated to apoint where the heavier hydrocarbons therein are almost vaporized; thelighter hydrocarbons are already vaporized in the heat exchanger. Thisprocess lowers the viscosity of the oil and promotes better filtration.

The heated hydrocarbon condensate is pumped by pump 149 through conduit170 to polycyclic aromatic removal assembly 180, comprising a pluralityof carbon filtration canisters 175, each containing activated charcoal;outlet 185 for a heated plasticizer oil end product; and a sensing meansfor sensing the differential pressure between the input side and theoutput side of the carbon filtration canisters 175. Polycyclic aromaticremoval assembly 180 removes colloidal contaminants, color bodies, andpolycyclic hydrocarbons from the heated hydrocarbon condensate. Anactivated carbon filter is preferred. In most cases, the carbonfiltration canisters will comprise a dual canister system in which thecanisters alternate between a stand-by mode and a filtering mode so thatcontinuous filtering can be maintained. The heated hydrocarboncondensate is pumped by pump 149 under pressure through the canisters.The sensing means monitors the differential pressure on the activecarbon filtration canister; when the pressure exceeds a threshold valueto indicate that the canister has reached its capacity, a signal isgenerated to either automatically switch to the unused canister or elseset an alarm for maintenance personnel to perform the switching action.It has been found that heated hydrocarbon condensate has a lowerviscosity which promotes better flow through the activated carboncanisters. Polycyclic aromatics are also known carcinogenic agents, andtheir removal by the polycyclic aromatic removal assembly 180 enablesthe system to meet governmental regulations for emissions and handlingof hazardous substances. Finally, the polycyclic aromatics are thesource of color in the hydrocarbon condensate, so that their removalalso results in a clear, colorless plasticizer oil which has high marketvalue. The hot plasticizer oil leaving outlet 185 is sent to a finalcooler or condenser (not shown) to cool the end product down to a pointwhere it can be safely handled.

The clear, colorless plasticizer oil leaving final cooler may be pumpedinto a storage facility from which it can be pumped into tank trucks ordrums for sale. It will be noted that plasticizer oil is a solvent witha moderate flash point; thus, the purified oil should be stored in afacility which is physically separate and removed from the Scrap RubberPyrolysis System. The purified plasticizer/extender oil produced by thissystem compares favorably to that produced by other conventionalpyrolysis systems. The purified oil has a lower viscosity. Suspendedsolids are eliminated and virtually all color is removed, producing anoil characterized by water white color and clarity. This “bright stock”has a market value substantially greater than fuel oil. Table 1 lists aset of measured characteristics of the plasticizer oil produced by theinvention. The plasticizer oil meets specifications of ASTM 104A of theAmerican Society for Testing Materials, i.e. composed of maximum of 20%aromatics, less than 20% paraffinic content, and remainder napthenics

TABLE 1 ASTM Test Method Property Value D-287 API Gravity 26 (Typical) —Density, lb./gal. 7.5 D-2161 Viscosity, SSU (100° F.) 120 (Typical)D-2161 Viscosity, SSU (210° F.) 40 (Typical) D-92 Flash Point, COC 330°F. (Typical) D-97 Pour Point −33° F. (Typical) D-1500 Color <0.5 D-611Aniline Point 169° F. (Typical) D-312D Sulfur, Wt. % 0.1 (Typical)D-2007 Aromatics, Wt. % 21.5% (Typical) D-2007 Saturates, Wt. % 78+(Typical)C. Carbon Black Purification and Refinement System

The Carbon Black Purification and Refinement System purifies and refinesthe crude granulated carbon black containing inorganic contaminants asprovided by the Scrap Rubber Pyrolysis System. Any crude carbon blackproduct having characteristics generally similar the that produced bythe invention can also be received by the system as well. The resultingend product is a carbon black having a structure similar to lowstructure furnace black of grade N326. Such furnace black is suitablefor use in inks and adhesives, molded rubber and plastic formulations,paints and other coatings. The preferred embodiment for this system isshown schematically in FIG. 5, to which reference is now made.

The crude carbon black provided by the Scrap Rubber Pyrolysis System ofthe invention is transferred therefrom by means of conveyor 210 whichdelivers the crude carbon black to an enclosed carbon black holding tank215. Conveyor 210 is preferably an auger-type conveyor which is enclosedto reduce dust and debris and also to promote safety. It should be notedthat holding tank 215 may receive crude carbon black streams from aplurality of Scrap Rubber Pyrolysis Systems which may be resident at thesame site or at different sites. In addition, holding tank 215 serves asa surge tank to allow temporary shutdown of either system.

From holding tank 210, the carbon black is metered for a constantcontinuous delivery by rotary valve 220 to the inlet 232 of mill 230.This mill is chosen to receive particulate matter and to reduce the sizeof the carbon black particles therein to a selected average size. Forexample, the average size of the aggregates of granular carbon blackproduced by the Scrap Rubber Pyrolysis System may be about 60 to 80 mesh(about 0.007-0.010 inch). The mill is selected to reduce the averageaggregate size to less than about 325 mesh (about 0.001 inch). An airpowered fluid energy jet mill assembly is preferred as jet mills arecapable of producing very fine powders, and air is received through airinlet 231. It has been found that a 100 psi air stream with dry airhaving a dew point of −50° F. or lower is preferred. This is due to thefact that carbon black powder has strong tendency to agglomerate in thepresence of moisture and the use of dry air prevents agglomerationproblems later in the system. An air-powered fluid energy jet millassembly is preferred. A suitable jet mill is a JET PULVERIZER brandmarketed by The Jet Pulverizer Company (Moorestown, N.J.).

Once pulverized, the carbon black powder can be efficiently handled by apneumatic conveying system which moves the carbon black powder indiscrete portions, i.e. slugs, between the subsequent processingcomponents. The movement of the slugs between components is accomplishedby using compressed aire from a common source. The conveyor employed canbe best described as a three stage, dense phase conveyor system asproduced several companies, such as Dynamic Air® Conveying Systems, St.Paul, Minn. The three conveyor phases for purposes of describing theremainder of the Carbon Black Purification and Refinement System are asfollows:

-   -   (1) phase one—conveyor between the jet mill 230 and rotary        screening device 250    -   (2) phase two—conveyor between rotary screening device 250 and        pelletizer 260; and,    -   (3) phase three—conveyor between pelletizer 260 and carbon black        storage tank 270.

The phase one conveyor 242 conveys the milled carbon black powder fromoutlet 233 of jet mill 230 to final screening assembly comprising ascreening device adapted to removed oversized particulate contaminants,such as fiberglass and silicon dioxide, and a magnetic separator 258 forremoving any remaining ferrous particles. The preferred rotary screeningdevice is a rotary screening device, such as the Centri-sifter producedby Kason Corporation, as modified to utilize a 325 mesh. The milledcarbon black powder enters inlet 252 of rotary screening device 250. Theoversized particulate contaminants captured in the interior 254 of therotary screening device as the finer carbon black powder is allowed topass through the 325 mesh screen to the exterior 256. These oversizedparticulate contaminants, may be disposed of at any solid wastenon-hazardous land fill. The milled carbon black powder also isprocessed for the removal of fine ferrous particles which were notremoved in the gross screening assembly in the pyrolysis system. Amagnetic separator 258 is used as a final attempt to remove any ferrousparticles such as iron, nickel and cobalt particles which remain.Various reliable magnetic separators are commercially available and aregenerally configured as a pair of ceramic plates on either side of thecarbon black stream. The ferrous particles removed by magnetic separator258 are easily collected on a regular basis, i.e. daily, and discarded.The order in which the carbon black powder is thus purified by therotary screening device 250 and magnetic separator 258 is not relevantand can be in reverse order without departing from the spirit of theinvention.

The phase two conveyor 244 conveys the screened and milled carbon blackpowder from the magnetic separator 258 to a pelletizer 260, comprisingan enclosed holding tank and a pelletizing device for forming compressedpellets of carbon black without a binder, i.e. “soft pellets”. Thepelletizing step reduces dust problems in shipment but is an optionalpart of the overall process. Any standard device known to the industrycould be used; preferred is a device of a type made by FeecoInternational or Ferro-Tech.

The phase three conveyor 246 then conveys the soft pellets of carbonblack powder from the pelletizer 260 to an enclosed carbon black storagetank 270. A weighing and packaging assembly 280 may be included forreceiving the carbon black pellets from the storage vessel andautomatically packaging the pellets for market in preselected amounts.Optionally, if the pelletizer is not implemented and carbon black powderis produced, then the weighing and packaging assembly 280 receivescarbon black powder from the storage tank 270 and automatically packagesthe powder, such as 50 and 100 pound bags or large containers.

Because the milling, separating, and conveying equipment employed inthis system is completely enclosed, no airborne carbon blackcontaminants are generated. Thus, a dust collection system is notusually necessary.

The milled and purified carbon black produced by this system comparesfavorably to carbon black produced by other systems. This milled,purified carbon black has a lower tar content and exhibits a lower heatloss factor at 105° C. The ash content is reduced primarily due to themore efficient removal of fiberglass and silicon dioxide particles, andthe percentage of fixed carbon is greater. Table 2 gives the typicalvalues found in the carbon black powder produced by this system.

TABLE 2 ASTM Test Method Property Value D1510 Iodine Absorption No 67±mg/gm D2414 DBP Absorption No 80± cc/100 gm D1618 Solvent Discoloration80% Transmittance (Min.) D1506 Ash Content 1.0% (Max.) — Zinc OxideContent 7.5% (Typical) — Sulfur Content 2.2% (Typical) D1509 HeatingLoss 0.2% (Max.) D1513 Pour Density 26 ± 2 lb./ft³ D1514 Sieve Residue:U.S. No. 35 1 ppm (Max.) U.S. No. 325 10 ppm (Max.) D1508 Fines Content(U.S. No. 120): Bulk 7% (Max.) Bags 12% (Max.) D3192 VulcanizatePurpoerties: (vs. IRB#6) 300% Modulus (30′), psi Tensile @ Break (30′),psi −250 (Typical) Elongation @ Break (30′), +300 (Typical) psi +20(Typical) Tint Strength Test (similar to 100 (Typical) ASTM D3265)**Developed by MONOCHEM Corp.

While only a preferred embodiment has been illustrated and described,obvious modifications may be made within the scope of this invention asdescribed without substantially changing its functions. Accordingly, thescope of the invention should be determined not by the embodimentsillustrated but by the functions they perform and their legalequivalents.

1. A system for processing scrap rubber to produce marketable endproducts, the system comprising: a. a scrap rubber pyrolysis system,comprising: i. a pyrolysis vessel receiving rubber shreds into a heatingzone within the vessel and passing the rubber shreds as a bed throughthe heating zone under a constant temperature condition so that eachportion of the bed remains within the heating zone for a constantresidence time of sufficient duration to allow for complete pyrolysis ofthe shreds into carbon black and pyrolysis gas and to allow fordesorption of the pyrolysis gas from the surface of the carbon black;ii. a centrifugal separation means for receiving the pyrolysis gas fromthe pyrolysis vessel and removing entrained carbon black particles fromthe pyrolysis gas; and iii. a condensate separation assembly receivingpyrolysis gas from the centrifugal separation means, the condensateseparation assembly comprising a condenser receiving pyrolysis gas fromthe centrifugal separation means, the condenser arranged to condense thepyrolysis gas into a hydrocarbon condensate fraction in a liquid phasecollected in a reservoir at a lower end of the condenser and a vaporfraction in a gas phase, wherein the vapor fraction contains entrainedhydrocarbon condensate droplets, and the hydrocarbon condensate fractionhas a selected composition determined by a selected equilibriumtemperature maintained at a surface of the reservoir; and a secondaryseparator receiving the vapor fraction and removing the entrainedhydrocarbon condensate droplets; b. a plasticizer oil purificationsystem comprising: i. a mixing vessel receiving hydrocarbon condensateand mixing the hydrocarbon condensate with a filter aid under conditionswhich aggregates of particulate contaminants in the hydrocarboncondensate and the filter aid are formed; ii. a filter aid removalassembly for removing the aggregates of filter aid and contaminants fromthe hydrocarbon condensate received from the mixing vessel; iii. apolycyclic aromatic removal assembly receiving the hydrocarboncondensate from the filter aid removal assembly and removing polycyclicaromatics from the hydrocarbon condensate; and c. A carbon blackpurification and refinement system comprising: i. a jet mill for millingthe carbon black into particles of a selected average size in thepresence of dry air; ii. a carbon black screening assembly adapted toseparate oversized contaminants from the milled carbon black; and iii. amagnetic separator adapted to remove ferrous particles from the milledcarbon black.
 2. The system of claim 1 wherein the centrifugalseparation means receiving the pyrolysis gas accelerates the entrainedcarbon black particles therein and allows the carbon black particles tobe removed from the pyrolysis gas by means of gravity.
 3. The system ofclaim 1, wherein the centrifugal separation means is a cycloneseparator.
 4. The system of claim 1 wherein the pyrolysis vessel furthercomprises a heating jacket and a plurality of burners within the heatingjacket, fuel to the burners being supplied by a first blower, air to theburners being supplied by a second blower, wherein an overabundance ofair is supplied to the burners to reduce the temperature of the burnerflame to less than 2000° F.
 5. The system of claim 1, wherein thecondenser is comprised of a condensing section having baffles and apyrolysis gas line for receiving the pyrolysis gas, the pyrolysis gasdirected across and over the baffles which are interposed within theflow path of the pyrolysis gas, the condensing section also having areservoir for collection of hydrocarbon condensate and a condensate linefor draining the hydrocarbon condensate from the reservoir, thecondensing section also having a vapor line for providing vaporcontaining entrained condensate droplets; a cooling section with acirculating heat transfer fluid, the cooling section disposed toencourage heat transfer between the pyrolysis gas and the heat transferfluid; a sensing means disposed to measure the equilibrium temperatureat the surface of the reservoir; a refrigeration unit receiving heattransfer fluid from the cooling section and sending the heat transferfluid to the cooling section at a selected fluid temperature; and, apump maintaining a flow rate of heat transfer fluid through the coolingsection responsive to the equilibrium temperature, wherein the flow ratevaries to maintain the hydrocarbon condensate fraction and vaporfraction at the selected equilibrium temperature while they are inequilibrium at the surface of the reservoir.
 6. The system of claim 1herein the carbon black screening assembly comprises: an oscillatingfine screening deck for separating oversized contaminant particles fromcarbon black received from the pyrolysis vessel; and, a magneticseparator for separating ferrous particles from carbon black receivedfrom the pyrolysis vessel.
 7. The system of claim 1 wherein the filteraid removal assembly comprises a rotary drum vacuum filter.
 8. Thesystem of claim 7 wherein the rotary drum vacuum filter comprises arotary drum with an outer surface and a scraping blade disposed alongthe outer surface to scrape aggregates from the surface as the rotarydrum rotates.
 9. The system of claim 1 wherein the polycyclic aromaticremoval assembly comprises activated carbon.
 10. The system of claim 1wherein the hydrocarbon condensate is heated prior to presentation tothe polycyclic aromatic removal assembly.
 11. The system of claim 1wherein the screening device in the carbon black purification andrefinement system comprises a rotary screening separator.
 12. The systemof claim 11 wherein the rotary screening separator contains a 325 meshscreen.
 13. A system for condensing pyrolysis gas obtained from a scraprubber pyrolysis system, the system for condensing pyrolysis gascomprising: a cyclone separator receiving the pyrolysis gas, wherein thecyclone separator removes entrained carbon black from the pyrolysis gas;a condenser receiving pyrolysis gas from the cyclone separator, thecondenser arranged to condense the pyrolysis gas into a hydrocarboncondensate fraction in a liquid phase collected in a reservoir at alower end of the condenser and a vapor fraction in a gas phase, whereinthe vapor fraction contains entrained droplets of hydrocarboncondensate, and the hydrocarbon condensate fraction has a selectedcomposition determined by a selected equilibrium temperature maintainedat a surface of the reservoir; a secondary separator receiving the vaporfraction and removing the entrained droplets of hydrocarbon condensate;a mixing vessel receiving the hydrocarbon condensate and mixing thehydrocarbon condensate with a filter aid under conditions which permitparticulate contaminants in the hydrocarbon condensate to formaggregates with the filter aid; a filter aid removal assembly forremoving the aggregates of filter aid and contaminants from thehydrocarbon condensate received from the mixing vessel; a means forheating the hydrocarbon condensate received from the filter air removalassembly; and, a polycyclic aromatic removal assembly adapted to receivethe heated pyrolysis oil from the filter aid removal assembly and toremove polycyclic aromatic contaminants from the pyrolysis oil.
 14. Thesystem of claim 13 wherein the polycyclic aromatic removal assemblycomprises activated carbon.
 15. The system of claim 13 wherein thefilter aid removal assembly comprises a rotary drum vacuum filter. 16.The system of claim 13, wherein the condenser is comprised of acondensing section having baffles and a pyrolysis gas line for receivingthe pyrolysis gas, the pyrolysis gas directed across and over thebaffles which are interposed within the flow path of the pyrolysis gas,the condensing section also having a reservoir for collection ofhydrocarbon condensate and a condensate line for draining thehydrocarbon condensate from the reservoir, the condensing section alsohaving a vapor line for providing vapor containing entrained condensatedroplets; a cooling section with a circulating heat transfer fluid, thecooling section disposed to encourage heat transfer between thepyrolysis gas and the heat transfer fluid; a sensing means disposed tomeasure the equilibrium temperature at the surface of the reservoir; arefrigeration unit receiving heat transfer fluid from the coolingsection and sending the heat transfer fluid to the cooling section at aselected fluid temperature; and, a pump maintaining a flow rate of heattransfer fluid through the cooling section responsive to the equilibriumtemperature, wherein the flow rate varies to maintain the hydrocarboncondensate fraction and vapor fraction at the selected equilibriumtemperature while they are in equilibrium at the surface of thereservoir.